Tetrahedral wiping pad

ABSTRACT

A blank of fluid-transmitting sheet material is formed into the shape of a tetrahedron filled with a fluid-absorbing mass such as textile fibers, to produce a wiping pad with four surfaces, of especial utility in the graphic arts.

United States Patent Mitchell [4 Mar. M, 11972 [54] TETRAHEDRAL WIPING PAD [72] Inventor: Philip A. Mitchell, East Walpole, Mass.

[73] Assignee: The Kendall Company, Boston, Mass.

[22] Filed: June 18, 1970 211 Appl. N0.: 47,431

[52] U.S.Cl. ..l5/ll8,5/337, l5/210R [51] Int. Cl. ..A47l 13/16 [58] Field of Search................15/208, 209 R, 210 R, 104.93, 15/104.94, 118, 244 B, 244 C; 5/337, 338; 128/270,

[56] References Cited UNITED STATES PATENTS 3,347,363 10/1967 Dyl-tes et a] ..D9/182 UX 3,396,420 8/1968 Mitchell ..15/210 2,958,885 11/1960 Donney ..15/244 B X FOREIGN PATENTS OR APPLICATIONS 244,001 2/ 1947 Switzerland ..15/209 R Primary Examiner-Daniel Blum Attorney-John F. Ryan 5 7] ABSTRACT A blank of fluid-transmitting sheet material is formed into the shape of a tetrahedron filled with a fluid-abs0rbing mass such as textile fibers, to produce a wiping pad with four surfaces, of especial utility in the graphic arts.

1 Claim, 8 Drawing Figures PAIENTEHMAR 14 I972 SHEET 1 BF 3 TE'IRAII'IEDRAL WIPING PAD This invention relates to an improved absorbent pad, and more particularly to a pad adapted for the application, spreading, and removal of various liquids used in the graphic arts trade, particularly in the art of lithographic reproduction.

In modern lithography, reproductions are made from spe' cially-prepared metal plates, the preparation of which involves numerous wet processing steps such as cleaning, etching, coating with lacquer, retouching, inking, and the like. Involved in these processing steps are the application and subsequent distribution or removal of various aqueous and organic solvent solutions, such steps being carried out in various sequences depending on the particular nature of the reproduction to be made. Conventionally, the distribution of the various liquids, and the removal of excess, is effected by the use of fabric rags, paper, wads of fiber, or nonwoven fabrics. Natural and cellulose sponges are used to some extent, but contamination of the sponge is common and the relatively high cost necessitates reuse.

The use of conventional wiping materials in the preparation of lithographic plates has two disadvantages. First is the danger that the conventional wiping material will shed lint, which is picked up by the plate surface, interfering with the development of a proper image. A second drawback in conventional wiping materials is that they are called on to perform two functions which are conflicting. First, they are used to spread a fluid evenly and uniformly over a metal plate, and with a uniformity which persists from plate to plate. Second, they are used to remove excess fluid from the plate, to leave a film which in final form may be less than one tenthousandth of an inch in thickness. A wiping material which has sufficient absorbent capacity and high capillarity to serve efficiently in the wiping-off process will absorb into itself an excessive amount of fluid and give a poor distribution of fluid in the spreading process. Conversely, materials which will spread a thin fluid film over a metal printing plate are generally incapable of sequestering excess fluid.

A third disadvantage of conventional wiping pads is that they are usually of a flat, two-dimensional design, difficult to manipulate without wrinkling or creasing. This recognized disadvantage has led to the use of various holders or devices around which a flat pad may be wrapped. Attempts have also been made to use circular or rectangular disks of absorbent material, of substantial thickness of up to an inch or more. Such expedients are cumbersome, uneconomical, or both.

It is an object of this invention to provide an improved lithographic wiping pad in the form of a tetrahedron, which as a single unit is simple to grasp and to manipulate, and which offers to the operator four working surfaces which may be employed seriatim in a sequence of wiping operations.

It is a further object of the invention to provide a tetrahedalIy-shaped wiping pad the four surfaces of which differ from one another in their absorbent capacities.

Other objects of the invention will be apparent from the following description and drawings, in which FIG. 1 is an idealized perspective view of the tetrahedral pad of this invention.

FIGS. 2, 3, and 4 are front, side, and top elevations respectively, of the pad of FIG. 1.

FIG. 5 is a perspective view of an initial stage in the formation of the pad of this invention.

FIG. 6 is a second stage in said formation.

FIG. 7 is a cross-sectional view of FIG. 5.

FIG. 8 is a perspective view of the pad in use.

Referring to FIG. I, the wiping pad I is shown as consisting of a blank of absorbent sheet material formed into a tetrahedron with a bottom face 12, side faces 14 and I6, and a top face I8, sealed into a unitary three-dimensional structure by means of the end seals 20 and 22. The pad is filled with an absorbent material such as textile fibers, thread waste, papermaking fibers, plastic foam waste fragments, or the like, textile-length fibers being preferred for reasons set forth more fully below. For the sake of clarity, the absorbent filling is not shown in FIG. I.

A preferred method of forming the tetrahedral pad is shown in FIGS. and 6. In FIG. 5, a generally cylindrical tube 24 of absorbent sheet material is shown, which :may be formed from a rectangular blank of sheet material sealed or sewn together along a pair of opposing edges (seam not shown). Altematively the tube may be of tubular knit or woven fabric, or a tubular film which is either naturally moisture-transmitting or apertured.

The tube 24 contains a filling or stuffing of a yielding and compressible absorbent mass 26 which in the preferred form comprises textile-length fibers, and will be referred to herein as the fibrous filler. A seal or seam 28 is formed at one end of the tube by flattening the top and bottom edges together, as shown in FIG. 6, said seal being conveniently formed by the jaws of a heat-sealing machine in case the sheet material of the tube is, for example, a heat'sealing nonwoven fabric. To complete the product, the opposing sides 30 and 32 of the other end of the half-sealed tube are brought together to be sealed or seamed to form a closure which is substantially normal to the original sealing operation, so that the opposing sealed edges are at right angles to each other.

Various other methods of forming three-dimensional tetrahedral wiping .pads will suggest themselves to those skilled in the art. For example, the empty tube may first be sealed at one end, after which the absorbent filler is stuffed into the tube and the second seal is made. Alternatively, the three pieces of an equilateral triangle of moisture-transmitting material may be folded up to be brought together at a point, followed by a seaming of the three edges. For economy and simplicity of operation, however, the tubular process first set forth above is preferred.

Nonwoven fabrics are the preferred sheet material employed in forming the tubular container, and they are preferably of the light weight type, 20 to 40 grams per square yard. For convenience, they may be of a heat-sealable nature, due either to the bonding agent employed, or to the presence of a certain percentage of thermoplastic fibers in the web from which the fabric is formed. Apertured nonwoven fabrics of the type described in U.S. Pat. No. 3,507,943, of Apr. 2l, I970, of common assignee, are especially suitable for the formation of the tubular containers used in this invention.

The useful advantages of the tetrahedral pad structure of this invention are several. First, it is inherently three-dimensiona], and no matter which of the generally flat four working surfaces is lowermost, the pad presents a sort of fiatiron shape with an elevated forward projection (17 in FIG. I) to be easily and comfortably grasped between thumb and forefinger, as shown in FIG. 8, and with the rest of the pad sloping rearwardly to the horizontal seam 22 of FIG. I, which fits against the heel of the cupped hand. Second, with its four essentially distinct working surfaces it can perform a multiplicity of functions in applying and spreading various fluids used in graphic arts, and then removing excess fluid by a turn of the pad to expose a fresh surface. Third, the fibrous or other absorbent mass contained in the pad need not be uniform in composition. FIG. 7 is a cross-section of the unsealed end of the tube M of FIG. 5. It is filled with a sector of absorbent, highly hydrophilic rayon fibers 34, and two sectors of hydrophobic polyester fibers 36, 36, of low absorbency. The sectors of the different fibers are so distributed that the final tetrahedral pad will offer the operator two surfaces which are backed up by rayon fibers which have a high absorbent capacity, and two surfaces which, though wettable, are backed up by fibers which have the capacity to spread fluids without absorbing them to the degree which rayon fibers do. Spreading and subsequent blotting surfaces are thus offered in a single pad.

For immediate identification of the nature of the surfaces, the fibers of different absorbent capacities may be dyed or pigmented in different colors, visible through the semi-transparent covering envelope.

A final but appreciable advantage of the tetrahedral pad over all other solid shaped wiping pads is that it offers the highest ratio of surface (working) area to volume of absorbent filler. The ratio of surface area to volume for a tetrahedron,

cube, and sphere are 14.7 to 1, 11.2 to l, and 8.1 to l, respectively. This means that to provide a given working surface area, it takes 31 percent more filler if a cube is used rather than a tetrahedron, and about 80 percent more filler if a sphere is used.

Although the pad of this invention has been described in connection with its application in the graphic arts, it will be obvious that its utility extends also to the application of various fluids or pastes used, for example, in furniture refinishing, and in general household cleaning, polishing, and scouring applications.

Having thus described my invention, 1 claim:

I. An absorbent wiping pad in the form of a three-dimen- 

1. An absorbent wiping pad in the form of a three-dimensional tetrahedron, said pad comprising a fluid-transmitting retaining cover formed into the shape of tetrahedron, said cover enclosing an absorbent filler mass capable of absorbing fluids, said absorbent filler mass comprising textile fibers, the fibers comprising said filler mass being of at least two types of fibers differing in fluid-absorbing power, and said fibers being so distributed that the fibrous absorbent mass contacting certain surfaces of the pad differ in absorbing power from the fibrous mass contacting certain other surfaces of said pad. 